1) Copies exactly count successive wide characters from the wide character array pointed to by src to the wide character array pointed to by dest. If count is zero, the function does nothing. The arrays may overlap: copying takes place as if the wide characters were copied to a temporary wide character array and then copied from the temporary array to dest.

2) Same as (1), except that the following errors are detected at runtime and call the currently installed constraint handler function:

src or dest is a null pointer

destsz or count is greater than RSIZE_MAX/sizeof(wchar_t)

count is greater than destsz (overflow would occur)

As with all bounds-checked functions, wmemcpy_s is only guaranteed to be available if __STDC_LIB_EXT1__ is defined by the implementation and if the user defines __STDC_WANT_LIB_EXT1__ to the integer constant 1 before including wchar.h.

2) Returns zero on success, returns non-zero on error. Also, on error, fills the entire dst up to and not including dst+dstsz with null wide characters, L'\0' (unless dest is null or destsz is greater than RSIZE_MAX/sizeof(wchar_t))